What is cardiac preload and what factors influence it?

Here's an explanation of cardiac preload:

• What is preload?

  • Preload is the load that determines the resting length of a muscle before it contracts. In the heart, it refers to the stretch of the ventricular muscle fibers at the end of diastole (filling phase).

• Cause of cardiac preload:

  • The primary determinant of cardiac preload is the amount of venous blood return to the heart. This venous return directly influences the end diastolic volume (EDV) and end diastolic pressure (EDP), both of which can be used to estimate the magnitude of the cardiac preload.

• Effects of cardiac preload:

  • An increase in cardiac preload leads to a more forceful ventricular contraction. This happens because increased preload increases the tension developed by the ventricular muscle and its velocity of shortening.